This proposal requests support for a conference, "Tissue Specific Expression of Cloned Genes," to be held August 9-11, 1985, as a satellite symposium of the Tenth International Congress of the International Society for Developmental Biology (ISDB) in Los Angeles, California (August 4-9, 1985). This conference has been organized in response to recent and rapid progress in understanding the molecular biological aspects of development in higher organisms. Much of this progress is the result of transferring cloned genes to animal cells and embryos, then analyzing the DNA sequences necessary for correct expression of the genes. Numerous studies have revealed the importance of controlling sequences known as "enhancers" that seem to play a role in tissue specific gene regulation. Other studies in progress are defining the precise DNA sequences responsible for enhancer function either in intact organisms (by gene transfer to embryos) or in differentiated cells (by gene transfer to cells in vitro). These recent results could have profound implications for understanding development. The purpose of this conference is to bring together researchers, clinicians, and students in the area of gene transfer in order to promote a timely synthesis of recent information about the identity and mechanism of action of DNA regulatory sequences and related factors that are important in normal development and differentiation, with particular emphasis on the mammal.